To secure his standing as the presumptive Republican presidential nominee, Mitt Romney has disowned every sliver of moderation in his record. He’s moved to the right on tax cuts and twisted himself into a pretzel over the health-care plan he championed in Massachusetts — because conservatives are no longer allowed to acknowledge that government can improve citizens’ lives.

Romney is simply following the lead of Republicans in Congress who have abandoned American conservatism’s most attractive features: prudence, caution and a sense that change should be gradual. But most important, conservatism used to care passionately about fostering community, and it no longer does. This commitment now lies buried beneath slogans that lift up the heroic and disconnected individual — or the “job creator” — with little concern for the rest.

Today’s conservatism is about low taxes, fewer regulations, less government — and little else. Anyone who dares to define it differently faces political extinction. Sen. Richard Lugar of Indiana was considered a solid conservative, until conservatives decided that anyone who seeks bipartisan consensus on anything is a sellout. Even Orrin Hatch of Utah, one of the longest-serving Republican senators, is facing a primary challenge. His flaw? He occasionally collaborated with the late Democratic senator Edward M. Kennedy on providing health insurance coverage for children and encouraging young Americans to join national service programs. In the eyes of Hatch’s onetime allies, these commitments make him an ultra-leftist.

I have long admired the conservative tradition and for years have written about it with great respect. But the new conservatism, for all its claims of representing the values that inspired our founders, breaks with the country’s deepest traditions. The United States rose to power and wealth on the basis of a balance between the public and the private spheres, between government and the marketplace, and between our love of individualism and our quest for community.